The present invention relates broadly to a preprocessing system and method for an optical pattern recognition system, and more particularly to a pattern enhancement system and method for an optical pattern processing or character recognition system.
The practicality of optical character recognition systems has been established by the number of machines in successful operation, although most have a limited capability and are used for only a limited or highly standardized character set. Typically, these machines are provided with a preprocessing system whose function is to treat the original input patterns or images so that the main problem, namely, that of recognition or identification, is mitigated. Generally these preprocessing systems have been categorized as those which attempt to render the pattern free of imperfections, and those which enhance the pattern, including those that are commonly called skeletonizing systems.
The enhancement of features such as edges or skeletons by prior art techniques, while improving the presentation of patterns for subsequent recognition, have been done on a less than optimum basis. Generally, the time consumed in enhancing the pattern is lengthy, the signal-to-noise ratio between the output pattern and its background is low, or the apparatus necessary to obtain enhancement is complex and expensive, to illustrate a few examples of the problems of the prior art.
It has been previously proposed to process the total pattern or subsections of the total in parallel in order to skeletonize the pattern in simulation of the operation of the human eye. By "parallel" is meant that all points in the pattern are sensed and presented to the processing apparatus simultaneously, in contrast to a serial or stepped examination of each point in the pattern. Such parallel preprocessing has in one form required an iteration technique in which the pattern is continually eroded until it stabilizes, i.e., no further points on the boundary can be removed. In an alternative approach, iteration is not used, and instead the outputs of the sensor propagate in parallel through layers of electrical circuits to obtain an enhanced or extracted pattern. While this latter approach appears to simulate the human visual system, in actuality, the time required to propagate the input signal to conclusion is quite lengthy, e.g., two seconds or higher. Both the iteration and parallel-propagation approaches are therefore not ideal from the standpoint of being adaptable with present-day, electronic systems, such as optical character recognition systems, where the data to be processed is voluminous and must be handled on a high-speed and essentially real-time basis.